The present invention relates to a battery temperature detecting device which is attached directly to the surface of a charged battery so as to permit a heat sensitive sensor to pick up the variation of temperature of the battery and the same is transmitted to an internal circuit of the charger.
Generally, the conventional chargers available in consumers' markets are equipped with different kinds of detecting means to check if a charged battery is electrically saturated. The prevalent art adopted in most conventional chargers is based on the fact that if a charged battery becomes saturated, the voltage thereof will drop rather than continuously rise even more electric energy is still charged thereinto; this is so called "-.DELTA.V" feature. This feature is effectively used to detect the condition of a charged battery.
This "-.DELTA.V" art is put into effect by first recording the voltage of a battery at time T1 and then recording the voltage thereof at consecutive time T2, afterwards, the recorded voltages are put into comparison, if the result indicates the latter voltage is smaller than the former, it stands for the battery having been fully, charged, and the charger is made to stop. To some special batteries, the voltage drop -.DELTA.V is too small to be easily detected, so the application of this art thereto becomes incapable, frequently resulting in the damage of batteries from electrical overcharge.
All the available rechargeable batteries have a common feature, i.e., whenever a battery is saturatedly charged, continuous charge will not raise the voltage of the battery afterwards, and the excessive electric energy is only converted into thermal energy or heat, resulting in the gradual rising of tempeature in the battery. So the heat in the battery can be used as a detected factor to determine whether a battery is charged to saturation. This feature can be applied solely or along with the -.DELTA.V art to better detect the saturation of a charged battery in order to fully protect the same from damage by excessive heat generated from overcharge or can prevent the battery from undercharge.
However, the battery temperature detecting devices of the prior art or the present invention must all be equipped with a heat sensitive sensor such as a thermistor or the like. The disposition of the heat sensitive sensor is critical to the quality of a battery temperature detecting device, and an improper location of the thermal sensor will often result in false detection of the operation temperature of a battery. For instance, a motion telephone is equipped with a high power charger the inner circuit of which is apt to dissipation of large amount of heat during charge operation, causing the interior and superficial temperature of the charger much higher than the charged battery itself. In that case, the detected temperature variation of the battery is not correct at all and the internal circuit of the charger is often mistakenly actuated.
To solve the preceedingly cited problem, the heat sensitive sensor can be disposed directly in the interior of a battery and is associated with the inner circuit of the charger via a T terminal when the battery is being charged so as to enable the heat sensitive sensor to truly reflect the temperature of the battery. But so produced battery is relatively expensive and is not well adapted to other kinds of charger.